Multiple agent chemotherapy has curative potential in some hematologic malignancies and advanced rapidly proliferating solid tumors. Curative chemotherapy has benefitted from the discovery of new, relatively non-cross resistant agents, and more effective use of existing agents. Interventions which increase the efficacy of conventional agents include more effective regimens for multiple drug administration, minimization of drug toxicities and increased use of adjuvant, surgical or radiation therapy.
Despite recent advances, patients with many types of malignancies remain at significant risk for relapse and mortality. After relapse, some patients can be reinduced into remission with their initial treatment regimen. However, higher doses of the initial chemotherapeutic agent or the use of additional agents are frequently required, indicating the development of at least partial drug resistance. Recent evidence indicates drug resistance can develop simultaneously to several agents, including ones to which the patient was not exposed. The development of multiple-drug resistant (mdr) tumors may be a function of tumor mass and constitutes a major cause of treatment failure. To overcome this drug resistance, high-dose chemotherapy with or without radiation and allogenic or autologous bone marrow transplantation is employed. The high-dose chemotherapy may employ the original drug(s) or be altered to include additional agents. The feasibility of this approach has been demonstrated for hematopoietic and solid tumors. The development of new drugs non-cross resistant with mdr phenotypes is required to further the curative potential of current regimens and to facilitate curative interventions in previously treated patients.
Recently, the in vitro anti-tumor activity of a novel class of natural products called illudins was examined in Kelner, M. et al., Cancer Res. 47:3186 (1987), incorporated herein by reference. Illudin S and M are two types of illudins known to exist. Illudins have a chemical structure entirely different from other chemotherapeutic agents. Illudin compounds were previously purified and submitted for evaluation to the National Cancer Institute Division of Cancer Treatment (NCI DCT) in vivo drug screening program but had a low therapeutic index in other experimental tumor systems in accordance with NCI studies. The extreme toxicity of illudins has prevented any applications in human tumor therapy.
Thus, there exists a need for chemotherapeutic agents which are toxic to tumors, and especially mdr tumors, and have an adequate therapeutic index to be effective for in vivo treatment. The subject invention satisfies this need and provides related advantages.